Japan's top tariff negotiator, Ryosei Akazawa, spoke with U.S. Commerce Secretary Howard Lutnick by phone twice on Saturday, an official said, as they try to iron out some of the most difficult issues in pursuit of a deal that will be beneficial to both countries.

Akazawa, who has extended his stay in Washington, spoke to Lutnick for about 15 minutes in the morning and about 20 minutes in the evening, the Japanese government said, adding Tokyo will continue to work "strenuously" with Washington toward an agreement.

Akazawa's calls with Lutnick came a day after they held a meeting that lasted about an hour, with sharp differences apparently remaining over U.S. President Donald Trump's hefty tariffs on foreign-made cars and auto parts.

In the ongoing negotiations, Japan has placed top priority on mitigating the impact of the Trump administration's increase in April of the tariff on imported automobiles to 27.5 percent from 2.5 percent.

Trump and his trade team have shown no signs of scrapping or lowering such sector-based tariffs, including on steel and aluminum, that the president has imposed on national security grounds.

Akazawa arrived in Washington on Thursday for his seventh round of ministerial meetings on tariffs with U.S. Cabinet members.

Akazawa, Japan's minister for economic revitalization, was initially due to leave for Tokyo on Saturday, but he extended his visit to explore a separate meeting with U.S. Treasury Secretary Scott Bessent.

The official said it remains unclear how long Akazawa will stay in the U.S. capital.